Certain surgical procedures, such as orthopedic surgery, generally involve preparing a particular bone for attaching a sizing guide to the particular bone and resecting the particular bone in order to fit it with a prosthesis. An example of one such procedure is found in connection with the GENESIS II® Total Knee System by Smith & Nephew.
In a procedure such as the GENESIS II® Total Knee System, the surgeon first flexes the knee to 70-90° and performs a longitudinal incision over the anterior aspect of the knee along the medial border of the patella. The surgeon then retracts the patella laterally. Using a drill, a hole is made into the distal femur for an intramedullary rod. A valgus alignment guide and anterior cutting guide are connected to the intramedullary rod and inserted into the distal femur. The surgeon resects the anterior femur using the anterior cutting guide and a conventional resecting stylus guide such as that illustrated in FIG. 1. A conventional stylus 10 generally includes a stylus body 12, stylus shaft 14, stylus arm 16, an arm knob 18, and a locking mechanism such as a screw 20.
After removing the intramedullary rod, valgus alignment guide, and anterior cutting guide, the surgeon attaches a femoral sizing guide to the distal femur. The femoral sizing guide may also include a sizing guide stylus, similar to the conventional stylus 10, for example, illustrated in FIG. 1, to assist in referencing a position. The surgeon utilizes the stylus to determine the size of the prosthetic component from indicia on the stylus shaft 14. Once a reference point is found with the stylus arm 16, the surgeon turns the locking mechanism 20, which locks the stylus arm 16 into place. An appropriate reading of the stylus shaft 14 is taken, the stylus and sizing guide are removed and a prosthetic component is then attached.
As stated above, generally a stylus is utilized by the surgeon to resect a bone while referencing an unaffected area of the bone. In the particular case of knee surgery, for instance, this may include the tibial plateau or the femoral anterior. To reference an unaffected area, the surgeon manipulates the stylus height relative to the bone by moving the stylus body up or down. Furthermore, the surgeon manipulates the stylus arm by the arm knob in the rotational and translational direction to obtain an appropriate reference for resecting. Once an appropriate reference is determined, conventionally, the surgeon utilizes a screw or cam-lock means to prevent the stylus arm from rotating in the translational or rotational directions. Alternatively, a spring may be conventionally utilized to provide resistance to rotation but not prevent rotation.
Current surgical techniques attempt to reduce ancillary tissue damage performed during a surgical procedure. Such minimally invasive surgical techniques have resulted in less disturbance and potential trauma to soft tissue which would have been either removed or moved for greater access to the surgical area of the body in conventional surgery. Minimally invasive surgical techniques have, however, created issues with respect to navigating and maneuvering instruments in the presence of soft tissue. For example, in orthopedic surgery, the stylus arm must be manipulated against unaffected areas of the bone under soft tissue.
Conventional stylus locking structures generally involve either several steps to lock the stylus arm or do not completely prevent stylus arm rotation. For example, locking with a screw or cam-lock involves the surgeon applying the necessary torque to ensure that the screw or cam-lock does not loosen while a reference is made for resecting. There is a danger that the surgeon may not sufficiently tighten or lock the screw or cam-lock means and the stylus arm, unknown to the surgeon, rotates during the procedure. Additionally, even if the surgeon sufficiently tightens the screw or cam-lock, the stylus arm may still become disengaged if the screw or cam-lock is jarred, or otherwise, during the procedure. Furthermore, as stated previously, the conventional spring mechanism only provides resistance to the stylus arm rotating and does not entirely prevent rotation in either the rotational or translational directions.
During minimally invasive surgical techniques, especially, soft tissue may cause pressure to be placed on the stylus arm and cause the stylus arm to change position. The soft tissue may also cause pressure to be placed on the stylus locking mechanism and cause the locking mechanism to become unlocked, thereby possibly allowing the stylus arm to change position and, possibly, without the surgeon's knowledge. The consequences of a stylus arm unintentionally or unknowingly rotating may impair the integrity of the particular orthopedic procedure or even the health and welfare of the patient. The surgeon, for instance, may be unable to make a correct resection due to the stylus arm rotating while the surgeon is determining a reference for the resection. Furthermore, a stylus arm that unknowingly rotates may cause the surgeon to choose an incorrectly sized prosthesis and prolong the surgical procedure or adversely affect the results of the procedure.
Therefore, there is a need for a stylus that will allow a surgeon to rotate the stylus arm in the rotational and translational direction and lock the stylus arm to a particular position, when desired, while preventing the stylus arm from becoming unintentionally or accidentally unlocked. Additionally, there is a need for a stylus in which a surgeon can easily and quickly lock the stylus arm and one that provides the surgeon with an indication that the stylus arm is indeed locked. Such devices can be particularly useful in minimally invasive surgery.